Concern over extremists planning attacks at the upcoming winter Olympics has Russian officials on high alert.

The Russian government is deploying more than 50,000 police and soldiers to guard the games.

But U.S. officials say the concern shouldn't so much surround Olympic sites as it should for areas around the Games.

"The greater threat is to softer targets in the greater Sochi area, and in the outskirts beyond Sochi, where there is a substantial potential for a terrorist attack," Matthew Olsen, director of the National Counter-Terrorism Center, warned.

On Thursday Russian authorities detained two brothers with ties to a terror group that's been threatening to attack the Games.

The men are suspected of transporting suicide bombers who attacked a train station in Volgograd last month that killed 34 people.